WPF Ribbon Tab view in Designer

You can also use the SelectedIndex property on the Ribbon to set which tab is the currently selected tab (0 being the first tab, 1 being the second, etc.)

<ribbon:Ribbon SelectedIndex="0" />

The only way I have found is to set the Selector.IsSelected property to true. This will cause the tab to become visible at design time.

<ribbon:RibbonTab Selector.IsSelected="True" ...